1. Field of the Invention
The present invention relates to a mounting structure of a blower for a vacuum cleaner, and more particularly to a mounting structure of a blower for a vacuum cleaner, comprising a mounting cover for fixing the blower to a body base so that the blower is structurally separated from a body cover.
2. Description of the Related Art
Generally, a vacuum cleaner generates a vacuum within its body using a blower, thereby sucking rubbish such as dust together with external air and collecting the sucked rubbish. Recently, vacuum cleaners have been developed so as to improve blast performance of the blower and reduce undesired noise generated by the blower.
FIGS. 1 and 2 are cross-sectional and plan views of a mounting structure of a blower for a conventional vacuum cleaner, respectively.
The conventional vacuum cleaner comprises a body, a suction device (not shown) connected to an intake port 11 of the body, a dust collection bag (not shown) installed within the body, and a blower 30 installed within the body. A vacuum is generated within the body. The suction device sucks rubbish such as dust on the floor together with external air using the vacuum. The dust collection bag serves to collect the sucked rubbish and pass the sucked external air through. The blower 30 generates a vacuum within the body so that the rubbish together with external air is sucked into the body via the suction device.
Herein, the body includes a body base 10 being opened to the outside at its upper surface, and a body cover 20 being put on the opened upper surface of the body base 10. The interior of the body base 10 is divided into a dust chamber 12 provided with the dust collection bag installed therein, an air supply chamber 13 provided with the blower 30 installed therein, and a cord room 14 incorporating a cord reel (not shown) for winding an electric wire supplying power to the blower 30 thereon. A dust collection hole 21 is formed at an area on the body cover 20, corresponding to the dust chamber 12 of the body base 10, thereby allowing the dust collection bag to be replaced with a new one. A dust chamber cover 22 is detachably disposed on the dust collection hole 21 of the body cover 20 so as to open and close the dust collection hole 21.
A filter 18 for purifying air flowing into the blower 30 is installed between the dust chamber 12 and the air supply chamber 13.
The blower 30 is installed behind the filter 18, and includes an impeller 32 for generating a vacuum within the body, and a motor 34 connected to the impeller 32 by a rotary axis 33, for rotating the impeller 32. When power is applied to the motor 34, the motor 34 operates at a high speed of more than approximately 30,000 rpm.
In order to protect the blower 30 from external impacts, the front external surface of the blower 30 is surrounded by a mounting packing 36, and the rear external surface of the blower 30 is surrounded by a sealing packing 37. The central external surface of the blower 30 is surrounded by a sound cover 38 so as to shield noise generated by the operation of the motor 34.
As shown in FIGS. 1 and 2, in the mounting structure of the blower for the conventional vacuum cleaner, first and second supporting ribs 15 and 16 are protruded from the bottom surface of the body base 10 so as to respectively support the front portion of the blower 30 surrounded by the mounting packing 36 and the rear portion of the blower 30 surrounded by the sealing packing 37. Further, first and second pressing ribs 25 and 26 are protruded from the inner wall of the body cover 20 so as to respectively press the front portion of the blower 30 surrounded by the mounting packing 36 and the rear portion of the blower 30 surrounded by the sealing packing 37. Thereby, the blower 30 is fixedly interposed between the body base 10 and the body cover 20.
The mounting operation of the blower 30 within the body base 10 and the body cover 20 of the vacuum cleaner is described as follows. First, the blower 30 is disposed on the first and second supporting ribs 15 and 16, and the body cover 20 is put on the body base 10. Then, the front portion of the blower 30 surrounded by the mounting packing 36 is pressed by the first supporting rib 15 and the first pressing rib 25, and the rear portion of the blower 30 surrounded by the sealing packing 37 is pressed by the second supporting rib 16 and the second pressing rib 26. Thereby, the blower 30 is fixedly interposed between the body base 10 and the body cover 20.
In the above-described mounting structure of the blower for the conventional vacuum cleaner, since the body cover 20 is structurally connected to the blower 30 by means of the first and second pressing ribs 25 and 26, oscillation or noise generated by the operation of the blower 30 resonates at the body cover 20, thereby generating more resonant noise and causing annoyance to users.
Particularly, FIG. 3 is a graph illustrating the oscillation frequency of the body of the vacuum cleaner generated by the operation of the blower, measured by an accelerometer at the center of the upper surface of the body. When utility power of 60 Hz is applied to the motor 34, the motor 34 rotates at a high speed of more than 30,000 rpm. At this time, a peak (a) is found at about a self resonance frequency (SRF) of the motor 34, and a peak (b) is found at a frequency of about 120, 240, or 360 Hz, corresponding to a harmonic frequency of the external power. Further, a peak(c) is found at a frequency of about 4,500 Hz. Such peaks (a, b, and c) found at specific frequency bands are audible to humans, thereby causing stress to users.
Herein, the SPF is defined by the below equation, and the impeller 32 has nine vanes. Therefore, the peak(c) is found at 4,500 Hz, obtained by multiplying the value of the SRF by the number of the vanes of the impeller 32.   SRF  =            rpm      frequencyofexternalpower        ⁢                   ⁢    Hz  